Your probs look twofold to me. Are the white spots on the leaves and stem kind of fuzzy or fluffy? If so, then that is mealybug, easily sorted with an application of provado ultimate bug killer. You MUST apply this after watering and not when the roots are dry. After a few days, you can wipe the leaves (and stems) clean of the bug residue (the dead ones tend to stick on due to thier wolly protective coating)
You may be surprised that I think your brown tips are more due to over-watering than under. Both will show brown tips, but I see some sickly yellow on one of the leaves, and the stems are still quite round and plump. With underwatering, the stems get a concave look, u-shaped in cross-section, and the weight of the fronds on the soft stem make them wilt. (conversely, overwatering will also do this, but takes longer, as it is the death of the roots that prevents the stems from taking up water.)
Cold damage can also look like this.
How long have you had the plant? Plants are notoriously wrongly watered from outlets like Ikea, B&Q, etc, and the damage could have been done before you bought the plant. It looks as though it is still in it's original pot.
Hold the pot firmly and grasp all of the stems together in the other hand, and pull the plant out of the pot. A healthy Kentia will have beautiful strong white roots covered with tiny hair-like roots around the outside of the rootball. If many of these are dark and slimy, or have a 'rotten' smell, the plant is over-watered. Take a pic of the rootball and post on here so I can see.
Kentias are prone to brown tips in a dry atmosphere, but this is confined to a few mm at the end and does not travel further up the frond.
When watering, check that the first inch of the compost is dry, first. Then water thoroughly to soak the compost. Allow water to sit in the outer pot for about 15mins, then POUR ANY EXCESS AWAY. Most plants are happier if their compost dries out a little between waterings, then get a good drench. The roots need air as well as water, and even those plants like ferns that like damp soil will not survive in a waterlogged pot.
Your watering intervals will vary depending on conditions and time of yr. Much less in winter or low light levels, or could be every day in bright hot conditions. Many of my houseplants only get watered once per month or less in winter. plants can usually recover from underwatering, but once a plant's roots have started to rot from overwatering, the plant will die.
Hope this answers your questions!