Response field:null | ThingSpeak API | Forum

Good morning to all.
I apologize for my bad English, I have translated with Google.
I am using the REST API in a project, in which I have an ESP8266 that performs measurements and sends them to two fields of a Thingspeak channel, and an apk that allows me to send data to that ESP8266 to set the time of a timer using two fields of the channel .
It happens that when writing a single field of the 4 of the channel, reading the channel info (from the link https://api.thingspeak.com/channels/ /feeds.json) returns only the real value of the last field updated and the others with a value of "null".
Example:

Write Channel: https://api.thingspeak.com/update?api_key=5SO213O2UFAIAYIQ&field1=10&field2=20&field3=30&field4=40
Response: 4
Read feed: https://api.thingspeak.com/channels/1093470/feeds.json?results=2
Response:
{"channel":{"id":1093470,"name":"Canal 4-Pruebas-2","latitude":"0.0","longitude":"0.0","field1":"Field Label 1","field2":"Field Label 2","field3":"Field Label 3","field4":"Field Label 4","created_at":"2020-07-03T15:25:32Z","updated_at":"2020-07-03T16:26:15Z","last_entry_id":7},"feeds":[{"created_at":"2020-07-03T16:31:30Z","entry_id":6,"field1":"15","field2":null,"field3":null,"field4":null},{"created_at":"2020-07-03T16:33:04Z","entry_id":7,"field1":"10","field2":"20","field3":"30","field4":"40"}]}

Write only field 1: https://api.thingspeak.com/update?api_key=5SO213O2UFAIAYIQ&field1=15&field2=25
Response: 5
Read feed: https://api.thingspeak.com/channels/1093470/feeds.json?results=2
Response:
{"channel":{"id":1093470,"name":"Canal 4-Pruebas-2","latitude":"0.0","longitude":"0.0","field1":"Field Label 1","field2":"Field Label 2","field3":"Field Label 3","field4":"Field Label 4","created_at":"2020-07-03T15:25:32Z","updated_at":"2020-07-03T16:26:15Z","last_entry_id":6},"feeds":[{"created_at":"2020-07-03T16:30:06Z","entry_id":5,"field1":"15","field2":25,"field3":null,"field4":null},{"created_at":"2020-07-03T16:31:30Z","entry_id":6,"field1":"15","field2":25,"field3":null,"field4":null}]}

Is there a way to update fields independently, so that when retrieving a Feed the values of the other fields are obtained ( no "null"?

Thanks for your time and attention.