I wish I could provide some input regarding the indoor photoperiod best appropriate for the pygmy sundews, but all mine were mostly grown outdoors except in the cold months. I hesitate to give newbie advise to a long time grower, but consider the isssues of substrate purity. I always tried to use well weathered peat in my mix for these Droserae, and with a higher silica sand ratio than for many other species in the genus. Seeing mosses sprout so early in the pot makes me wonder. Nutrition as well may play a role in the lack of growth. Over heating is not good for these plants and can stimulate dormancy, and stipular development is an indication of impending dormancy. Wet and hot in a terrarium is contraindicated if dormancy is near. Many of the pygmy species I grew did go dormant in the summer months, and showed the best growth between March and June when the photoperiod was naturally less than 16h and the temps averaging in the 70F range. I found all the species always did best outdoors and speculate that a naturally increasing and decreasing photoperiod might be why. Few growers adjust their light periods, and the natural adjustments in daylength may contribute to their well being, just as has been discussed with the Petiolaris group, where someone speculated that an extended photoperiod might be a dormancy trigger. Gut level feelings tell me that your plants are headed towards dormancy....you don't list the affected species, but some pygmys are very sensitive during their mandatory summer dormancies and need both drier conditions and increased air circulation. Drosera mannii is one I could see the tag on, and that one fits the bill. I suggest (with some trepidation) that you try to maintain moisture deep in the pot while allowing the surface to become nearly dry, and keep the air moving as best as you can. Humidity is not wanted or needed during dormancy. Most growers want to grow their dews "wet" but the pygmy species are drought tolerant in the extreme, and I've had them growing in nearly bone dry substrates. For the summer sensitive species, I found indoors close under lights with a fan worked best, vs outdoors. I believe I used about 16h and with a gradual reducition over the summermonths until fall when good growth was again noted prior to gemmae production. I hope this helps amigo!