Hi, look at percentages you improved by 2,5% roughly that’s already quite good for a 4 week training! on this thread already performance improvement was discussed a bit.
Keep training! 
Giving it some thought also of course if you’re cold or too cold some of you energy will be used to keep your body warm! so that could affect, also what type of trainer you have? if not direct drive, (a wheel on turbo) then temperature has more impact on the power readings, maybe you need to calibrate the trainer.