I have only been keeping sun corals, dendros, and rhizos for about a year, but from what I have learned. Every flavor reacts differently to different things. Dendros and rhizos seem to follow the same exact rules.
1) Yelllow and orange are much more forgiving.
2) Small changes in water parameters, especially salinity make them pretty unhappy. I have noticed mine tend to do slightly better around 1.023 than 1.026..but the difference is only noticable because I spend too much time paying attention to them.
3) Larger, healthy colonies are able to withstand changes in many aspects, much better than smaller colonies
3) Even my healtiest colonies will go through periods where they tenticles appear more shriveled and generally are not quite as 'sticky' as you put it. Generally (assuming all other factors are good), I see new heads appear within the next week or two. Not sure exactly what the correlation is, but thus far, I contribute this to growth. Again, i don't notice this as much on larger colonies, but is very prevalant on smaller colonies.
4) Don't overfeed. This can cause stress on the coral, as it will try to consume everything you feed it. I have had bailout from too much feeding.
5) don't underfeed..obvious reasons.
5) I find that food about the size of Ocean Nutrition Mysis is about the right size. I feed many differeing types of meaty foods, but all about that size and seem to be consumed well.
6) Some people subscribe to lots of small particles in the water, I find they do fine with reasonable feedings every 2-4 days.