Several things help tighten bird feathers.
1st: Changing seasons especially cooler weather. For this reason, my aviary windows are open and evening temperatures are now down to low 60 or high 50 F degrees. Nothing like a cool breeze to tell us and the birds that show season and winter is coming.
2nd: Make sure the birds are healthy. The best product for building the immune system is Dr. Rob Marshall's KD powder, available from Lady Gouldian Finch. It should be used two consecutive days in the water and is effective at promoting overall strength and development of immunity to a variety of types of organisms.
3rd: Optimal nutrition. Start with overall vitamin products such as Orlux Omi-vit, Boost, Pro-vital or similar multiple vitamins. Keep a close watch for proper wing carriage and the a tight narrow piped tail. Wide tails or poor wing carriage or loose feathers is a sign that we need to do more.
For difficult cases or special birds feed CeDe Hand Rearing Formula (Higgins sells it.) and/or Harrisons High Potency best or Adult mash.
4th: Add Liquid B to the water. This really helps tighten them up! Over night the results are amazing.