My sebaes' tentacles inflate and deflate, but I think you are on the right track with the feeding and slowly increasing the light period. Try doing smaller more frequent water changes as well, like once a week or every 2 weeks. The trace elements quickly get used up, especially if you are skimming heavily. If you are not already doing it, soak the food in a vitamin supplement like selcon or vita-chem before feeding. Keep us posted and take more pictures to compare.