Hi princessk- I grow cyms outside and they do very well down here. Is there a reason why you have your cym inside versus outside? They do much better outdoors in bright light but not direct sun and need cooler night temperatures in the Fall to set flower spikes. Most indoor settings do not allow for this drop in temperature. Your SF weather will suit this plant just fine!
Cyms like to be potbound and a bit crowded in their pot, so I would wait until after flowering next season, if you do get flowers next year. Mike above pointed out that cym potting soil can look a bit like 'dirt', when it actually is more of a peat mix which is okay. (holds more water) Watering them is only a bit different from phals; they do not like to dry out completely (like phals) but want a bit more moisture near the roots. When you do water them, pour lots of water in from the top until it is thoroughly saturated and let it drain well from the bottom. Cyms are also heavy feeders and like fertilizer year round, but with your burnt tips I would back off for a while. Better not enough fert then too much. I mix a little Osmocote in with my mix which is a good slow-release fertilizer and I also mist them with worm tea, which is big on this forum!
Ask lots of questions and we will do our best to help you and your Grandmother's orchid through this transition!