From my research nail issues can commonly show up with increased stress (emotional or physical- crossfit anyone? ;), sickness or malabsorption of nutrients. While Paleo is awesome, we are all different and have different digestive 'situations', lives and relative nutrient needs. You may need to change up your diet a bit to include a few of the key components your body is currently in need of.
I've had increasing vertical ridges in my nails for years- it wasn't until after I was diagnosed Celiac that I did the research that indicated that mine were most likely due to nutrient malabsorption, particularly the B vitamins ( especially B12) and potentially iron.
In the last 6 months I've done several things (in addition to going Paleo) that I credit with helping greatly reduce the ridges...
- B vitamin shots 1- 2x per month. I get the B12, B1, B6 and folate combo... Often these will be offered at a local community health store.
- sublingual B vitamins for better absorption- Sprouts has one with B12, B6 and folate.
- digestive enzymes and HCL with each meal to increase nutrient/mineral absorption
- probiotics- both transient ones like lacto and bifidio strains and some of the the longer term colonizers (Prescript-assist or Bio-Kult have some). Note: most supplements only have the transient species which are great helpers, but only stick with you for about a week before heading out. These bacteria help us by producing a constant stream of vitamin k and b vitamins. Nice lil guys...
- prebiotic & probiotic 'living' foods like sauerkraut, kombucha, kefir...
- reduced physical and emotional stress- including cutting back on my excessive workout schedule.
From what I've read it can take a while to get back to smooth nails- anywhere from months to years depending on the severity of your case. Mine are already greatly improved, especially after the regular B vitamin shots. Hope this helps.
NOTE: I have seen multiple doctors that assured me that the ridges were common and 'no big deal' (they said that about my initial celiac symptoms as well) , but their resolution after going gluten free and adding some key nutrients makes it seem likely to me that they are indicative of some low to moderate level of malabsorption. Probably not a HUGE worry, but something to pay attention to.
Here are a few quick links for general overview, unfortunately I don't have time to look up any pubmed goodies' so these will have to do ;)
Note: I've also seen vertical ridges mentioned in rare cases as a result of kidney issues- probably not the case for you, but always good to know.