I am new to the orchid world and it started when I bought a plant at Meijer and I have had it for about three weeks now. Since then I have bought two other plants off of orchids.com and they have done really well until recently. I think that one may be sunburnt or maybe the water quality is bad(?). The one I'm refering to is the Dendrobium which i will show you now:
This is the full size of the plant itself:
These are the possible sunburn spots that I was refering to. Also as you can see some of the leaf tips are starting to turn brown and there is this white, chalky type of something that is on the leaves had has been ever since they have arrived in the mail:
This is what the potting material looks like. It is in a very small plastic pot and I'm not sure if it needs to be repotted or not:
I'm not sure if it's because of too much water, too much sun, or just bad water quality. I have not yet fertilized this plant in any way since I recieved it. I had it on a humidity tray but took it off as soon as I noticed this spot. I also noticed this spot on another leaf earlier. The entire leaf ended up turning yellow and I just pulled it off very easily. What can I do? Thank you in advance for any help that you can provide.