I do not understand what is going on. Tell me if anyone else experiences this issue and what they have found the problem to be.

I have a lot of new growth starting to grow on my grapefruit and orange tree..You know that tender light green growth. The for some reason all of a sudden they all start to curl up before the leaves mature. I have checked for insects always the first thing in my mind , and of course I found some. So I treated the trees with neem oil and soapy water and they are gone. Then rinsed the leaves off in shower so tender leaves will not be affected by the oil. Now some of the leaves are growing and some are just falling off..The new growth is falling off. NOt the old growth. It is as if some of the little tiny new leaves hardened then just fall off.Sometimes I touch the little growth and it just breaks off. Sometime 2 the very tip of the new growth will turn black them it grows to taller. Just the very minute tip leaf. Also the new growth grows no taller and stunts further height.I do not understand this. It never happens when they are growing outside though. Every winter when they are in the house the new growth has a problem maturing.

My room as plenty of light. SUN and 1000 watt grow lights, 450 watt grow lights and 600 watt grow light are on at least 8 hours a day. plenty of humidity too since the hunidity is kept up to 60-80- percent at all times with lots of fan breezes. Temp in that room is usually kept at 60's night and 70's by day. Perfect growing enviroment. If I was over watering the old growth would be falling off. I am having a problem with keeping the new bright green baby growth to continue growing taller. Some of the new growth does mature though....HELP . I also have lots of flush growth just not growing the way I want it to. Thanks for all the support all of you! :-)