I have several thoughts but have company coming. If you have time, please check the underside of leaves for mites, using magnification. Who ever said a comma isn't important? Hopefully, you'll have an answer because that's sure to come up.

Not to worry about the yellow dots, they are lithocysts, a normal morphological part of plants in the family Moraceae (mulberry) to which Ficus belongs.

Al

A new leaf popped out with edema which is fine. I don't see any symptoms of oedema, but I might have missed them or they aren't showing up in the images.

Very recently, a few days ago, I´ve transferred it from soil to semi hydroponic in leca and during my inspection for development I´ve realized the reddish dots were more predominant under the leaves. I'm curious re why you chose to change from a solid medium to water. Nearly any environmental condition that puts the brakes on growth and the accompanying use of sugars, but does not limit sugar production (photosynthesis) can cause anthocyanin buildup and purple leaves. This usually clears up as the leaf matures or as cultural conditions improve..

Also there was these yellow tiny dots which I started to notice after transfering but were there before as I can see it in the older picture. As noted above, the yellowish dots are called lithocysts. Within each of the lithocysts is a crystalline structure of calcium carbonate or calcium oxylate called a cystolith. Normal to Ficus.

Now, I do not have a special fertilizer for the fiddle fig, I´m using the same I use for all plants the General Hydroponics 3 part plus Diamond Nectar 0-1-1, Rapid Start 1-0.5-1 and CaliMag 1-0-0. For all I use 1 tablespoon per gallon less the Rapid Starter which I use half of a tablespoon. I´ve watered it when in soil a few times with this solution before transferring to leca and was ok. If you're happy with how your fertilizer supplementation program is going and want to stay with it, no need to change anything. I personally think it's a lot of excess outlay and effort that is going to be difficult to justify in the face of something simpler and less expensive ..... not that you should feel you need to justify anything at all. I'm just thinking about how a conversation between a hydro fertilizer salesman and me might go. Foliage-Pro 9-3-6 is a soluble synthetic which contains all nutrients essential to normal growth (taken up via the root pathway) in a single package, and supplied in a ratio at which the average plant actually used the nutrients. I suggest you give that a try for a few months and see how you fare. You'd have to fight me for mine.

.... also grow lights that goes on during the day and proving an extra 2h (about 14h of light), humidity relatively high (varies between 70% something to 90%). I don´t see any major red flags. The plant should show its appreciation for the added light and high humidity. Good work.

Can you help figuring this out and if a nutrient deficiency how can I use the fertilizers that I do have in a more balanced way. If you're reluctant to try the Foliage-Pro, let me know and I'll dig into it and figure out what should work.

I also use tap water ..... and I always filter it first and I usually have the water filtered a day before so there´s no chlorine on it. Not that it matters a whole lot, but few municipalities use chlorine gas any more to chlorinate. Other sources of chlorine have half lives measured in weeks, so leaving water out actually concentrates the amount of chlorine as the water evaporates and leaves the chemicals behind. Too, water from the cold water tap holds as much oxygen as it will likely ever have, straight from the tap. Free oxygen gasses off with time (overnight) and as the temperature rises. The dissolved oxygen would be considered a resource beneficial to root function.

Sorry, I forgot you have the tree in water. Strike what I said about dissolved oxygen as it applies to your tree. I'll leave the info though, because it might be valuable to you or others who might read this post.

Al

I put it at direct sunlight for a while because I wanted the new leaves to grow used to stronger light.

==>>

unless it was grown in full sun.. and most greenhouses are NOT sunny.. then you burned the leaves ..

study up on hardening off plants to new locations and plant culture variables..

first.. bring to home .... and let it rest and acclimate for a week or 3 .. lets say get over he stress of shipping from grower.. to seller.. and then the move to your house .... ... then move to higher light .. but not direct for 2 weeks.. then higher.. and then some time a few months later.. full sun if you wish ... same with temps.... etc ...

on some level you loved it to its detriment... lets try to avoid that next time...

ken

It happened to my fiddle too. i chopped it

There is no evidence to be seen in the images of sunburn (photo-oxidation) on the plant.

Now, is the worst time of year to chop a plant back if only for the fact the plant's response will be more lethargic than at any other point in the growth cycle.

Al