You could try packing clay dirt around the bottom edges. I have a raised bed garden that is enclosed by a cage and pavers in between the beds. I built a berm around the edges of the cage and pavers by packing dirt, watering it, packing tighter, watering etc etc. It almost acts like concrete.

Also, seed packets often put "days to maturity" without explaining that what they mean is actually days to maturity from "transplant". If you started from seed, 70 days could translate to 100+ days.

What did you use to fill the raised bed(s)? You should treat it as if it were a container and use a suitable mix that won't compact like heavy soil does. This can be affecting your plant growth.

How old is the manure and what exactly is your definition of "premium garden soil?" Was the manure fresh or composted before you added it? Does the Premium soil contain peat, vermiculite and/or perlite? Any compost added?

Have you ever done a soil test or had one done at your county extension service or agri university?

Fist let me said I did not know your contractor. But I did design my own beds. None of my raised bed were level at the bottom. They are all level at the top. I designed them that way to compensate the slope of the hill, without too much work or soil disturbance (call me lazy I don't mind).

What everyone already said here were all great points. Just want to add when I purchased the planting mix, I was told the soil was mixed with compost etc to aid aeration, thus will dry out faster. For me, the soil compacted over time and the problem improved. Raised beds get hot and dry out sooner. All my tomato plants were much happier in the raised bed. Yet all my cool season veggies seem to be going slower than planted in flat ground. I can't speak to your soil or moisture. But maybe you can call the place that sold you the soil and find out more details about the mix.

You should turned the soil over and mixed all the manure and the rest on the top in the begining.
Horse manure has lots on nutrients for you plants,
but your poor plants cannot get to it when they are small.
Most horse manures are alreadt mixed with a lot of stuff.
So they are not that strong to burn plants, ESPECIALLY when you till it in and mix with more soil.