Feeding the Masdies

[Intruder]

Since many years I search on the Net what is a good regime for feeding the Masdevallia.
I read the most various opinions and often very diverging.
This last in date from a renowned producer (on its site):
"Fertilizer: as with most orchids the mantra is “weekly, weakly”. We fertilize once a week at a low rate of 100 parts per million nitrogen".
Is that a low rate ??
If the maths are correct this mean 750 to 850 ppm of total salts (in function of the percentage of Nitrogen in the fertilyser). It seems to me a little bit high .
On Wiki I read: They should be fertilized with a half-strength mixture of a balanced fertilizer once a month and a high nitrogen fertilizer can be used for single applications in the spring and fall.
How high is a full strengh ??
Here in Belgium a nursery recommend 65 ppm N from a 13_3_15 Ca Mg one time per week. I have tested ... roots burn!
So in touch with your experience can you recommend me a level of feeding and a frequency which would be completely allowable to feed Masdevallia without the risk of burning roots or seeing appearing black stains on leaves. Thank you in advance.