the soil looks quite compact in the second picture. If ph etc. is ok I would suggest repotting with a well draining and airy mix and gently massaging the root ball to loosen up the soil.

when plants are in pots the roots make the soil more and more compact as they develop. The result is less and less air to the roots, less nutrient uptake etc. etc. It appears as if your plants suddenly hit a brick wall in development so you start ferting/flushing etc. usually only making things worse. :weedpoke:

good luck